Method for forming a tube and a method and a packaging machine for forming a package

A packaging machine for producing sealed packages of a pourable product from a web of packaging material advancing along a web advancement path, the packaging machine comprising:

• a conveying device for advancing the web of packaging material along the web advancement path at least to a tube forming station at which the web (4) of packaging material is formed, in use, into a tube;
• a tube forming device configured to form the tube at the tube forming station by overlapping a first lateral edge of the web of packaging material with a second lateral edge of the web of packaging material for obtaining a longitudinal seam portion of the tube;
• wherein the second lateral edge is arranged within an inner space of the tube after formation of the tube;
• wherein the first lateral edge comprises an internal outer surface facing the inner space and the second lateral edge comprises an external outer surface facing the internal outer surface, wherein during formation of the tube, the second lateral edge delimits an inner area of a partially formed tube;
• a sealing device configured to longitudinal seal the seam portion by fusing the internal outer surface and the external outer surface with one another;
• wherein the sealing device comprises a heating device configured to directly heat the external outer surface of the second lateral edge without heating the internal outer surface of the first lateral edge;
• and
• wherein the heating device faces said external outer surface of the second lateral edge and is entirely located outside of the inner area of the partially formed tube.

A method for forming a tube of a web of packaging material, comprising:

• advancing the web of packaging material along a web advancement path, the web of packaging material comprising a sealing strip;
• overlapping a first lateral edge of the web of packaging material with a second lateral edge of the web of packaging material to form a tube comprising a longitudinal seam, the tube comprising an inner space;
• wherein the second lateral edge is arranged within the inner space after formation of the tube;
• wherein the first lateral edge comprises an internal outer surface facing the inner space and the second lateral edge comprises an external outer surface facing the internal outer surface of the first lateral edge and an inner surface facing the inner space after formation of the tube;
• wherein the sealing strip comprises a first portion applied to the inner surface of the second lateral edge and a second portion that protrudes away from the second lateral edge, the sealing strip comprising a first face applied to the inner surface of the second lateral edge and a second face opposite to the first face;
• fusing at least the internal outer surface and the external outer surface with one another to longitudinally seal the seam portion of the tube;
• directly heating the external outer surface of the second lateral edge;
• heating by contact the internal outer surface by establishing contact between the internal outer surface and the directly heated external outer surface;
• and
• wherein, during the step of directly heating, the second portion of the sealing strip is directly heated and, subsequently, fused to the internal outer surface on said first face of the sealing strip.